Active Vibration or Sound Absorption Method with Virtual Resonators Exclusively using Sensing Coil&#39;s Current and Voltage

ABSTRACT

The invention discloses an active vibration or sound absorption method with virtual resonators exclusively using sensing electromagnetic coil&#39;s current and voltage. The invention includes an absorption actuator, a sensing module of coil&#39;s current and voltage, an absorption controller, and a driving module. The method controls the coil current&#39;s phase to be orthogonal to the actuator velocity&#39;s phase, to adjust the resonant frequency of the actuator, such that the signal to be absorbed causes a resonance in the actuator. In this way, a virtual resonator is formed. Moreover, one actuator can generate multiple virtual resonators simultaneously to absorb energy of multiple signals with different frequencies, and the resonant frequency and its damping ratio for each virtual resonator can be adjusted independently.

TECHNICAL FIELD

The invention is related, in general, to the field of active sound or vibration absorption and active control of sound or vibration suppression.

BACKGROUND OF THE INVENTION

All kinds of sound or vibration absorbers or attenuation suppressors are widely used in various engineering practices. However, there is a lack of high-quality sound or vibration absorbers or attenuation suppressors with simple structures, excellent performance, and stable convergence for multiple frequencies and varying frequencies. This patent precisely meets this demand.

SUMMARY OF THE INVENTION

The patent discloses a method which adjusts a resonant frequency of the actuator by controlling the actuator's coil current, such that the resonant frequency is consistent with the frequency of the signal to be absorbed. As a result, the signal to be absorbed causes resonance in the actuator, and the resonant cavity is realized virtually. In this way, the signal energy to be absorbed is collected and absorbed by the virtual resonant cavity. Moreover, a damping ratio of the virtual resonant cavity can also be adjusted independently. In addition, the absorption method with the virtual resonators uses an adaptive control algorithm, to actively absorb signal energy with multiple frequencies and frequencies that can be perturbed, based only on the measured coil current's signal and coil voltage's signal. The method is composed of an absorption's actuator, a sensing module of the coil current and voltage, an absorption's controller, and a driving module. The absorption's actuator faces the propagation's direction of the signal to be absorbed, and the sensing module of the coil current and voltage feeds the measured coil current and voltage to the controller. Meanwhile, the absorption's controller outputs a control signal amplified by the driving module to drive the coil of the actuator. Generally speaking, an absorbed source signal usually contains multiple frequency harmonics, and each frequency harmonic which needs to be absorbed corresponds to a virtual resonator. This method is to decompose the absorbed source signal into multiple single-frequency signals, and each of them corresponding to a virtual resonator, and each resonant frequency and damping ratio of the virtual resonator are adjusted according to each decomposed single-frequency, respectively. Finally, each individually controlled output is superimposed and sent to the driving module. Thus, the controller performs adaptive algorithm control on multiple frequencies and variable frequencies for absorption signals. As a result, the energy of the signal to be absorbed will be collected by the virtual resonator and converted into electromagnetic energy to be stored, while mechanical energy to be lost. In this way, the expected function of absorbing signal energy is implemented.

FIG. 1 describes, in detail, the working principle and structural block diagram of the method. First, the controller 100 is connected to the driving module 210 and the sensing module of current and voltage 220. The sensing module of current and voltage 220 measures the coil current and voltage's signals amplified by the driving module 210 configured to drive the absorption's actuator 300, and the measured results are fed back to the controller 100; in addition, the controller 100 includes a calculation module of absorption harmonic 110, calculation module of adjustment residual 120, and an adaptive control module 130; the actuator 300 includes a magnet 310 and a coil of wire 320, an equivalent spring 330, an equivalent mass 340 and an equivalent damping 350. The drawings contain reference marks description and reference variables description.

A theoretical derivation of energy absorption method with virtual resonators and an adaptive control algorithm of the absorption method are presented as below.

1. Energy Absorption Method with Virtual Resonators

The motion equation of moving part of the actuator is:

${\left( {{m_{a}S} + c_{a} + \frac{k_{a}}{S}} \right){v_{a}(s)}} = {{F_{e}(s)} + {F_{p}(s)}}$

The electromagnetic force caused by the coil current is divided into two parts. One part is used to adjust the resonant frequency of the moving part of the actuator, represented by I′_(coil); the other part is used to adjust the resonant damping ratio of the moving part of the actuator, expressed by I″_(coil). It is expressed as:

F_(e) = C_(e)Bl ⋅ I_(coil)(s) = C_(e)Bl ⋅ (I_(coil)^(′)(s) + I_(coil)^(″)(s)) ${\left( {{m_{a}S} - {\frac{C_{e}{Bl}}{S \cdot {v_{a}(s)}}{{I_{coil}^{\prime}(s)} \cdot S}} + c_{a} - {\frac{C_{e}{Bl}}{v_{a}(s)}{I_{coil}^{''}(s)}} + \frac{k_{a}}{S}} \right){v_{a}(s)}} = {F_{p}(s)}$

Let's define

${\left( {{m_{a}^{\prime}S} + c_{a}^{\prime} + \frac{k_{a}}{S}} \right){v_{a}(s)}} = {F_{p}(s)}$ ${\left( {{m_{a}S} + c_{a}^{\prime} + \frac{k_{a}^{\prime}}{S}} \right){v_{a}(s)}} = {F_{p}(s)}$

wherein

${m_{a}^{\prime} = {m_{a} - \frac{\Delta^{\prime}}{S}}}{c_{a}^{\prime} = {c_{a} - \Delta^{''}}}{k_{a}^{\prime} = {k_{a} - {\Delta^{\prime}S}}}{\Delta^{\prime} = {\frac{C_{e}{Bl}}{v_{a}(s)}{I_{coil}^{\prime}(s)}}}{\Delta^{''} = {\frac{C_{e}{Bl}}{v_{a}(s)}{I_{coil}^{''}(s)}}}$

Assuming the phase of I′_(coil) is orthogonal to the phase of ν_(a), so m′_(a) or k′_(a) is real, then the natural frequency of the actuator after adjustment is:

$\left( \omega_{n} \right)^{2} = {\frac{k_{a}}{m_{a} - {{❘\Delta^{\prime}❘}/\omega_{n}}} = \frac{k_{a} + {{❘\Delta^{\prime}❘}\omega_{n}}}{m_{a}}}$

wherein

${❘\Delta^{\prime}❘} = {{m_{a}\omega_{n}} - \frac{k_{a}}{\omega_{n}}}$

Assuming again that I″_(coil) and ν_(a) are in phase or opposite phase, then c′_(a) is real, the resonant damping ratio of the actuator is:

$\xi = {\frac{c_{a}^{\prime}}{c_{a,c}^{\prime}} = {\frac{c_{a}^{\prime}}{2\sqrt{k_{a}m_{a}^{\prime}}} = \frac{c_{a} - \Delta^{''}}{2\sqrt{k_{a}m_{a}^{\prime}}}}}$

wherein

Δ″=c _(a)−2ξ√{square root over (k _(a) m′ _(a))}

The resonant angular frequency of the moving part of the actuator is:

ω_(r)=ω_(n)√{square root over (1−2ξ²)}

The expected regulation current for the resonant frequency ω_(n) is:

${\hat{I}}_{coil}^{\prime} = {\frac{v_{a}}{C_{e}{Bl}}{\left( {{m_{a}\omega_{n}} - \frac{k_{a}}{\omega_{n}}} \right) \cdot e^{j\omega_{n}}}}$

The expected regulation current for the resonant damping ratio ξ is:

${\hat{I}}_{coil}^{''} = {\frac{v_{a}}{C_{e}{Bl}}\left( {c_{a} - {2\xi\sqrt{k_{a}\left( {m_{a} - {{❘\Delta^{\prime}❘}/\omega_{n}}} \right)}}} \right)}$

The expected total coil regulation current is:

Î _(coil) =Î′ _(coil) +Î″ _(coil)

The expected coil regulation voltage is:

{circumflex over (V)} _(dr) =C _(d) Bl·ν _(a) +Î _(coil)(R _(c) +SL _(c))

Since the velocity of the actuator cannot be changed suddenly, the residual of the regulating voltage is:

e _(dr) ={circumflex over (V)} _(dr) −V _(dr)=(Î _(coil) −I _(coil))(R _(c) +SL _(c))

For the case where a signal to be absorbed contains multiple frequency harmonic components, according to the principle of superposition, each absorption frequency corresponds to a virtual resonator, and various variables related to the virtual resonator are also decomposed into corresponding harmonic components, which are expressed as follows:

F _(p)=Σ_(k) F _(p,k)

ν_(a)=_(k)ν_(a,k)

{circumflex over (V)} _(dr)=Σ_(k) {circumflex over (V)} _(dr,k)

Î _(coil)=Σ_(k) Î _(coil,k)

Î′ _(coil)=Σ_(k) Î′ _(coil,k)

Î″ _(coil)=Σ_(k) Î″ _(coil,k)

In this way, the adjusted voltage residual corresponding to the k^(th) resonant frequency ω_(r,k) is:

e _(dr,k) ={circumflex over (V)} _(dr,k) −V _(dr,k)=(Î _(coil,k) −I _(coil,k))(R _(c) +SL _(c))

2. Adaptive absorption control algorithm

Defining the sensing latency relationship for the coil voltage and current as:

=e ^(jφ) ^(dr,k) ^(sen) ·V _(dr,k)

=e ^(jφ) ^(coil,k) ^(sen) ·I _(coil,k)

To adjust the latency for each frequency harmonic component to satisfy:

φ_(dr,k) ^(sen)−φ_(coil,k) ^(sen)=φ_(dr,k) ^(adj)−φ_(coil,k) ^(adj) =Δt _(sense)/ω_(r,k)

where Δt_(sense) is a difference between the measured voltage latency and the measured current latency.

Defining amplitude-phase relationship for the driving module as:

V _(dr,k) =A _(dr,k) ^(dri) ·e ^(jφ) ^(dr,k) ^(dri) ·V̆ _(dr,k)

Improved DXHS adaptive algorithm:

${{{\overset{\smile}{V}}_{{dr},k}(n)} = {{A_{{dr},k}(n)} \cdot {\sin\left\lbrack {{{\omega_{r,k}(n)} \cdot T \cdot n} + {\phi_{{dr},k}(n)}} \right\rbrack}}}{{A_{{dr},k}(n)} = {{A_{{dr},k}\left( {n - 1} \right)} + {\Delta{A_{{dr},k}(n)}}}}{{\phi_{{dr},k}(n)} = {{\phi_{{dr},k}\left( {n - 1} \right)} + {\Delta{\phi_{{dr},k}(n)}}}}{{\Delta{A_{{dr},k}(n)}} = {{- \mu_{r}} \cdot {e_{{dr},k}(n)} \cdot {\sin\left\lbrack {{{\omega_{r,k}(n)} \cdot T \cdot n} + {\phi_{{dr},k}(n)}} \right\rbrack}}}{{\Delta{\phi_{{dr},k}(n)}} = {{- \mu_{p}} \cdot {e_{{dr},k}(n)} \cdot {\cos\left\lbrack {{{\omega_{r,k}(n)} \cdot T \cdot n} + {\phi_{{dr},k}(n)}} \right\rbrack}}}{{\omega_{r,k}(n)} = {{\omega_{r,k}\left( {n - 1} \right)} + {\Delta{\omega_{r,k}(n)}}}}{{\Delta{\omega_{r,k}(n)}} = {{\mu_{f} \cdot \Delta}{{PH}_{{dr},k}(n)}}}{{\Delta{{PH}_{{dr},k}(n)}} = {{{\left( {1 - \lambda} \right) \cdot \Delta}{{PH}_{{dr},k}\left( {n - 1} \right)}} + {\lambda \cdot {{\Delta\phi}_{{dr},k}(n)}}}}{{{Wherein}e_{{dr},k}} = {{{\hat{V}}_{{dr},k} - V_{{dr},k}} = {\left( {{\hat{I}}_{{coil},k} - I_{{coil},k}} \right)\left( {R_{c} + {SL}_{c}} \right)}}}{{\hat{I}}_{{coil},k} = {{\hat{I}}_{{coil},k}^{\prime} + {\hat{I}}_{{coil},k}^{''}}}{{\hat{I}}_{{coil},k} = {\frac{v_{a,k}}{C_{e}{Bl}}{\left( {{m_{a}\omega_{n,k}} - \frac{k_{a}}{\omega_{n,k}}} \right) \cdot e^{j\omega_{n,k}}}}}{{\hat{I}}_{{coil},k}^{''} = {\frac{v_{a,k}}{C_{e}{Bl}}\left( {c_{a} - {2\xi_{k}\sqrt{k_{a}\left( {m_{a} - {{❘\Delta_{k}^{\prime}❘}/\omega_{n,k}}} \right)}}} \right)}}{{❘\Delta_{k}^{\prime}❘} = {{m_{a}\omega_{n,k}} - \frac{k_{a}}{\omega_{n,k}}}}{\omega_{n,k} = \frac{\omega_{r,k}}{\sqrt{1 - {2\xi_{k}^{2}}}}}$

The measured latency Δt_(sense), the control algorithm latency Δt_(control) and the driving phase shift Δφ_(dr) all have an effect of phase shift on the absorption control algorithm. The novelty and advantages of the improved DXHS adaptive control algorithm can automatically adjust to compensate for the effect of phase shift.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following embodiments, the specific implementation details for system configuration requirements, system parameter correction, startup of the virtual resonator, acquisition of the signal spectrum to be absorbed, system application scenarios, and key steps of absorption method are described as below:

1. System Configuration Requirements

a). Absorptive Capacity Analysis

-   -   Let the maximum disturbance pressure that the absorber expects         to absorb be p_(max). Also suppose that the maximum         electromotive force that the absorber can provide is F_(elc)         ^(max), to make the absorber absorb the vibration caused by the         disturbing force, it must satisfy F_(elc) ^(max)>S_(a)·p_(max)     -   That is,

$I_{coil}^{\max} > \frac{s_{a} \cdot p_{\max}}{C_{e}{Bl}}$

-   -   Suppose the nominal power and pressure sensitivity of the         absorber are W_(rate) and SPL_(1w) respectively, and the maximum         absorbable pressure level is:

SPL _(max)=20·log₁₀[p _(max) /p _(ref)]

-   -   wherein

p_(ref) = 2 × 10⁻⁵Pa SPL_(max) = SPL_(1w) + 3 ⋅ log₂W_(rate) $p_{\max} = {10^{\frac{{SPL}_{\max}}{20}} \cdot p_{ref}}$

-   -   The maximum pressure of the absorber obtained from the above         formula should be verified by testing.

b). Requirements for Sensing Module and Driving Module

-   -   The current measurement latency and voltage measurement latency         of the sensing module should be as close as possible, and as         small as possible. The driving latency of the driving module         should also be as small as possible, and the relationship         between phase shift and signal frequency be as smooth and         consistent as possible.

c). Selection of the Controller

-   -   Select a processor with real-time computing capability and         sufficient computing capacity as the central processing         component of the controller, such as Field-programmable gate         arrays (FPGA) and system-on-chip (SOC)s.

2. System Parameter Correction

a). Coil Electrical Parameters R_(c), L_(c)

-   -   From the initial state of the coil zero current and zero         voltage, apply a constant coil voltage V_(dr). After the coil         current I_(coil) stabilizes, measure V_(dr) and I_(coil), then         obtain R_(c)=V_(dr)/I_(coil). After obtaining R_(c), apply the         constant coil voltage V_(dr) from the initial state of the coil         zero current voltage. For the initial stage of applying the         constant coil voltage, I_(coil) is relatively sufficiently         small, there is below relationship:

$L_{c} = {\left( {\frac{V_{dr}}{I_{coil}(t)} - R_{c}} \right)t}$

-   -   R_(c), L_(c) can be obtained by impedance analyzer.

b). Coil Electromagnetic Parameters C_(e)Bl

-   -   First, place the absorber on a rigid non-vibration platform, and         use the accelerometer method or the dual-microphone reflection         method to measure the relative velocity ν_(a) of the actuator.         Since the sensing module can directly measure V_(dr) and         I_(coil), the parameters can be written as:

${C_{e}{Bl}} = \frac{{V_{dr}(s)} - {{I_{coil}(s)}\left( {R_{c} + {S \cdot L_{c}}} \right)}}{v_{a}(s)}$

c). Actuator Resonant Frequency ω_(r)

-   -   To use a driving firmware to short the two ends of the coil to         Ground, there are:

${F_{e}(s)} = {{C_{e}{{Bl} \cdot {I_{coil}(s)}}} = {\frac{{- C_{e}}{{Bl} \cdot C_{d}}{Bl}}{\left( {R_{c} + {SL}_{c}} \right)}{v_{a}(s)}}}$ ${\left( {{m_{a}S} + c_{a} + \frac{C_{e}{{Bl} \cdot C_{d}}{Bl}}{\left( {R_{c} + {SL}_{c}} \right)} + \frac{k_{a}}{S}} \right){v_{a}(s)}} = {F_{p}(s)}$

-   -   Then to use a frequency generator to generate test excitation         signals to find the resonant frequency ω_(r) corresponding to         the maximum resonant velocity ν_(a). Wherein, ν_(a) can be         calculated by the coil current:

$v_{a} = \frac{- {I_{coil}\left( {R_{c} + {S \cdot L_{c}}} \right)}}{C_{d}{Bl}}$

d). Actuator Damping Ratio ξ

-   -   First, use a driving firmware to short the two ends of the         electromagnetic coil to ground; second, the pressure amplitude         p_(a) acting on the actuator is measured by a pressure sensor.         Since the velocity of the actuator is:

$v_{a} = \frac{- {I_{coil}\left( {R_{c} + {S \cdot L_{c}}} \right)}}{C_{d}{Bl}}$

-   -   Therefore, the damping ratio can be calculated by the following         formant ratio:

$M_{r} = {\frac{1}{2\xi\sqrt{1 - \xi^{2}}} = \frac{{v_{a}(s)} \cdot k_{a}}{\omega_{r}p_{a}A_{s}}}$

e). Sensing Latency Difference Δt_(sense)

-   -   Define Δt_(sense) as the difference between the coil voltage         sensing latency and the coil current sensing latency.     -   First, attach a relatively large mass object to the moving part         of the actuator and then apply a relatively small driving         voltage V_(dr). For this situation, E_(d)(s) can be approximated         to zero, and the latency equations can be written as:

V _(dr)(s)=I _(coil)(s)(R _(c) +SL _(c))

e ^(−j(φ) ^(dr) ^(sen) ^(−φ) ^(coil) ^(sen) ⁾·

=

·(R _(c) +SL _(c))

e ^(−j(Δt) ^(sense) ^(/ω) ^(e) ^()·)

⁼

^(··(R) _(c) +jω _(e) L _(c))

The sensing latency difference Δt_(sense) can be obtained by the above formula, where

is the measured coil voltage,

is the measured coil current, and ω_(e) is the excitation frequency. Parameters

,

and ω_(e) can be measured.

3. Startup for Virtual Resonator

The startup process of the virtual resonator is as follows:

-   a). First, to obtain resonant frequency ω_(r) and damping ratio ξ     for the virtual resonator to start operating; -   b). To apply an electromagnetic excitation force with the resonant     frequency of ω_(r), apply an electromagnetic coil excitation voltage     V_(dr) ^(i). The amplitude of which is from zero initial value and     is sufficiently slow increased; -   c). Use the measured values of the electromagnetic coil current and     voltage to calculate the velocity ν_(a) of the actuator; -   d). Calculate the resonant frequency adjustment current I′_(coil)     and damping ratio adjustment current I″_(coil,k), according to the     velocity ν_(a) of the actuator, and then obtain the corresponding     coil adjustment voltage V′_(dr) and V″_(dr); -   e). Apply the total control regulation voltage V_(dr)=V_(dr)     ^(i)+V′_(dr)+V″_(dr) to generate a working virtual resonator; -   f). Based on the latest velocity ν_(a) of the actuator, adjust the     electromagnetic excitation voltage ν_(dr) ^(i), such that ν_(a) is     allowed in the specified range; -   g). After the velocity ν_(a) of the actuator oscillates stably, the     starting process of the virtual resonator is completed.

4. Acquisition of Spectrum to be Absorbed

The steps of using the virtual resonator's resonant frequency scanning method to obtain the spectrum of the signal to be absorbed are:

-   a). Select the lowest frequency of the signal to be absorbed as the     initial scanning frequency of the virtual resonator; -   b). After the virtual resonance occurs and stabilizes, record the     coil excitation voltage V_(dr,0) ^(i), the velocity of the actuator     ν_(a,0), and resonant frequency ω_(r,0); -   c). Stop applying coil excitation voltage V_(dr,0) ^(i), resonant     frequency adjustment voltage V′_(dr,0), and damping ratio adjustment     voltage V″_(dr,0), then the virtual resonance will be stopped; -   d). Select the next frequency scanning point to startup a virtual     resonance. When the virtual resonance is stable, record the coil     excitation voltage V_(dr,k) ^(i), the velocity of the actuator     ν_(a,k), and the resonant frequency ω_(r,k), then stop the virtual     resonance; -   e). Continue select next frequency scanning point and repeat the     above step until the highest absorption frequency; -   f). Calculation of the signal spectrum:

${\left( {{m_{a}S} + c_{a} + \frac{k_{a}}{S}} \right){v_{a}(s)}} = {{F_{i}(s)} + {F_{\omega}(s)} + {F_{\xi}(s)} + {F_{p}(s)}}$ ${\left( {{m_{a}^{\prime}S} + c_{a}^{\prime} + \frac{k_{a}}{S}} \right){v_{a}(s)}} = {{F_{i}(s)} + {F_{p}(s)}}$

-   -   Resonant peak ratio:

$M_{r} = {\frac{1}{2\xi\sqrt{1 - \xi^{2}}} = {❘\frac{{v_{a}(s)} \cdot k_{a}}{\omega_{r}\left( {{F_{i}(s)} + {F_{p}(s)}} \right)}❘}}$

-   -   K^(th) order resonant peak ratio:

$M_{r,k} = {\frac{1}{2\xi_{k}\sqrt{1 - \xi_{k}^{2}}} = {❘\frac{{v_{a,k}(s)} \cdot k_{a}}{\omega_{r,k}\left( {{F_{i,k}(s)} + {F_{p,k}(s)}} \right)}❘}}$

-   -   Given known ξ_(k), ν_(a,k), k_(a), ω_(r,k), and F_(i,k), from         the above formula, F_(p,k) (s) can be) calculated, which is a         point in the signal spectrum.

5. System Application Scenarios

a). Vibration Absorption Application

-   -   When applying invention to absorb vibration signals, for objects         to be absorbed, typical application examples include tube wall         of air conditioners or a casing of power equipment. The         vibration absorbing actuator can be installed both inside and         outside the tube wall of air conditioners or the casing of power         equipment. Inside installations may not require more space, but         may be difficult to maintain. Outside installations may require         more space, but is easy to maintain. For vibration absorption         applications, a loudspeaker or an actuator functionally         equivalent to a loudspeaker can be used as an actuator of         vibration absorber, and the method needs to determine required         actuator power, frequency spectrum range, number of actuators,         and location of actuators according to specific vibration         absorption requirements. The vibration source causes the base of         the actuator to vibrate, so that the moving part of the actuator         moves relative to the base of the actuator.     -   For a specific application, selection of vibration absorption         capacity of the actuator can be determined by the calculation         method and experiment method. The calculation method requires         the stiffness and mass distribution of the object to be         absorbed. After measuring the motion of different measuring         points of the object to be absorbed, the equivalent disturbance         force on the measuring point can be obtained by calculation. The         number of vibration actuators and its distribution should         satisfy that the maximum vibration displacement caused by         multiple distributed vibration actuators for any point on the         object to be absorbed is greater than maximum vibration caused         by the maximum disturbance force excitation in the case of no         vibration actuators, and within the disturbance frequency range.         The experimental method is to select different actuator powers,         different numbers of actuators, and different actuator         distributions, and a combination thereof that meets the above         requirements.

b). Sound Absorption Application

-   -   When applying invention to absorb sound signals, a typical         application example is to absorb sound in cab or power machine         room. For implementation of this type of sound absorption         system, a loudspeaker or an actuator functionally equivalent to         a loudspeaker can be used as actuator of sound absorber. The         power rate of the actuator, spectrum range of sound absorption,         number of the actuators, arrangement of the actuators and its         orientation should be determined according to the specific         requirements of sound absorption application.     -   Similar to above vibration absorption application, this design         configuration of sound absorption system can also be carried out         by the calculation method and experiment method. The calculation         method requires the intensity and distribution of the sound to         be absorbed. The number of sound absorbers and its distribution         should satisfy that, in the case of no disturbance and within         the disturbance frequency range, the maximum sound pressure         caused by multiple distributed sound absorbers, at any point on         the range of the sound absorption area, is greater than sound         pressure caused only by the excitation of the largest disturbing         sound source without any sound absorber. The experiment method         is to select different sound absorber power, different number of         sound absorbers, and different sound absorber distribution, and         a combination thereof that meets above requirements.

6. Key Steps of the Absorption Method

The vibration and sound absorption method of the invention adjusts the resonant frequency and damping ratio of the actuator by controlling and I′_(coil) and I″_(coil), to obtain a bandpass filter with adjustable center frequency and bandpass width, equivalent to a Helmholtz resonator with adjustable parameters. After completing the system configuration and parameter correction, the system is ready to perform vibration or sound energy absorption. The key steps of the energy absorption mainly include the following three aspects:

a). Determining Absorption Frequencies

-   -   First, use the resonant frequency scanning method with the         virtual resonator to obtain a spectrum of signals to be         absorbed, and then determine the frequency of absorption and the         number of the absorption frequencies.

b). Determining Absorption Damping Ratio

-   -   Before the signal to be absorbed causes the virtual resonator to         resonate, set the damping ratio to be smaller, so that the         signal to be absorbed can excite the virtual resonator resonance         as quickly as possible. After the virtual resonator resonance         occurs, adjust the absorption damping ratio, such that the         resonant velocity of the actuator is within the allowable range.         On the other hand, it is necessary to adjust the resonant         velocity of the actuator to be as high as possible, as the         greater the resonant velocity of the actuator, the more energy         will be absorbed.

c). Tracking of Frequency Disturbance or Drift

-   -   The adaptive control algorithm in this method has frequency         tracking capabilities for a disturbance of frequency. In         addition, the resonant frequency of the virtual resonator can         also be adjusted by comparing the difference between the         resonant frequency and the frequency corresponding to the         measured or calculated maximum velocity peak. 

What is claimed is:
 1. An active vibration or sound absorption method with virtual resonators exclusively using sensing coil's current and voltage, including an actuator, a sensing module of coil's current and voltage, a controller, and a driving module, to control coil current's phase to be orthogonal to velocity's phase of the actuator to adjust the resonant frequency in the actuator, such that a signal to be absorbed causes a resonance in the actuator to form the virtual resonator.
 2. The method according to claim 1, furthermore, the controlled electromagnetic coil's current is divided into two parts, where phases are orthogonal to each other, one of which is orthogonal to actuator velocity's phase, configured to adjust resonant frequency of the actuator, while the other of which is in phase or antiphase with the actuator velocity's phase, configured to change a resonant damping ratio of the virtual resonator.
 3. The method of claim 2, wherein, while applying the coil control current for adjusting resonant frequency, needs to impose an excitation voltage to the electromagnetic coil with the same resonant frequency to start a virtual resonator to work as expected.
 4. The method of claims 2 and 3, furthermore, in order to maximize energy absorption, it is necessary to adjust resonant damping ratio of the virtual resonator, such that the actuator's velocity reaches the maximum within an allowable range.
 5. The method of claims 2, 3 and 4, furthermore, one actuator can generate multiple virtual resonators simultaneously, to absorb energy of signal harmonics with different frequencies, and the resonant frequency and damping ratio for each virtual resonator can be adjusted independently. 